Kyle J. Marsh
Vineet Maheshwary
Amy Kopin
December 13, 2005
APD2005-04
The Village Well
Using Wind to Provide Clean Water for People in Developing Countries
1
Kyle J. Marsh
Vineet Maheshwary
Amy Kopin
December 13, 2005
APD2005-04
The Village Well
Using Wind to Provide Clean Water for People in Developing Countries
Thousands die every year in developing countries by ingesting polluted and dirty water; to respond to this, we have designed a windmill system to be used to pump fresh water in remote locations of the developing world. We have based our design off of the highly versatile Nicaraguan rope pump, and have designed it to compete with the AMEC rope windpump. What follows is a description of the situations and environment the project will be used in, whom the project will effect, and whose needs will be fulfilled. In addition, we have included a comparison of different types of vertical shaft windmills and an explanation of our design objectives. Concept generation and engineering and economic analysis of the system are included. Finally, we outline our implementation process and establish a business and marketing plan which will enable successful production of our system.
1. Introduction
1.1...... Definition of Needs
1.2...... Benchmarking Studies
1.2.1...... Social Context
1.2.2...... Existing Products
1.3...... Design Objectives
1.3.1...... Sizing System
1.3.1.1...... Assess the water requirement
1.3.1.2...... Find Pumping Depth
1.3.1.3...... Evaluate Wind Resource
1.3.1.4...... Estimate Size of Wind Machine
1.3.2...... Other Objectives
2...... Concept Generation
2.1...... Alternative Concepts
2.1.1...... Windmill Basics
2.1.2...... Types of VAWT’s
2.2...... Concept Selection Process
2.3...... Design Concept
2.3.1...... Preliminary Design
2.3.2...... Revised Design
2.3.3...... Final Design
2.3.4...... Prototype
3...... Engineering Analysis
3.1...... Formulation of Engineering Equations
3.2...... Establishment of Optimal Rotor Design
3.3....Engineering Optimization using Excel Solver
3.4...... Load Matching of System
4...... Economic Analysis
4.1...... Micro Economic model
4.1.1...... Demand Model
4.1.2...... Revenue Model
4.1.3...... Cost Model
4.2...... Outcome of Economic Model
4.3...... Design Impact of Economic Analysis
5...... Marketing Analysis
6...... Product Development Process
7...... Broader Impact
8...... Conclusions
9...... Appendix
9.1...... Nomenclature
9.2...... Business Plan
9.2.1...... Business Opportunity
9.2.2...... Business Objective
9.2.3...... Product Description
9.2.4...... Market Analysis
9.2.5...... Financial Data
9.2.6...... Supporting Documents
9.2.7...... Technical Analysis and Benchmarking
9.3...... Scenario
9.4...... References
9.5...... Other
1. Introduction
1.1Definition of Needs
Throughout the developing world, the supply of fresh water is a great concern. Paulo Lugari of Gaviotas said “Progress should not be measured by the number of hospital beds an area has, but by the number of cups of fresh water” 1.
People often settle near streams and rivers, and in fact the way most people live is a sort of symbiosis with the river itself; food and water are both linked to it, and it is both a rejuvenating and cleansing effect. As populations swell, however, the demand on these rivers becomes greater, and the waters become more and more tainted. This tainted water often carries waterborne diseases which infect those who come in contact with them; in fact, waterborne diseases are the single largest killers of infants in developing countries --diarrhea alone causes 4 million deaths a year2 -- and access to safe water correlates strongly with the survival of children under five years old. An alternative source of fresh water reduces the chances at passing along these diseases and significantly improves the health of the local population.
"Like energy, the need for water is increasing rapidly as supplies of traditional resources continue to diminish due to overuse, waste, and pollution. Unlike energy, the ability to harness local resources to produce water is not possible. However, we do have the capability to use local energy resources to gain access to water supplies that would otherwise be unavailable. This water is either located underground in deep aquifers or in surface lakes, rivers, and streams. In many cases, the absence of available, inexpensive energy makes gaining access to this water expensive, time consuming, and potentially dangerous. The proper application of any number of energy options today can be made gaining access to this water a reality in many areas not previously considered"23.
Wells provide a source of water when there is no river nearby, but they can also provide access to naturally filtered groundwater when located within the floodplain. To combat the problem, then, of unsafe water in the rivers we have agreed that the most practical solution to provide clean water to developing countries is to help communities construct wells that are pumped by wind power. This relatively simple technology should instead be part of an educational process that not only improves the living conditions of the communities effected but also raises the consciousness of all those involved. In that respect, we have approached this project proposal from the standpoint of an activist group that will be developing an effective design that can be produced cheaply, locally, and simply, and can be taken into these developing areas and shared with the people there as part of an educational and peacekeeping mission.
The benefits of fresh water have already been established and include improved health for all who draw from the well. There are other benefits to a windmill/ well campaign aside from the public health context: by reaching out to these isolated groups, and introducing them to the concepts of technology and engineering, science and machinery, we can begin to raise awareness of the outside world. Due to the distances between villages, many of these groups live as cultural islands, isolated from their neighbors. Not only will a windmill campaign provide fresh water but it will provide fresh social connections.
1.2Benchmarking Studies
1.2.1Social Context
Hand pumps can be ideal for single families or a few households in rural areas if the hydraulic equivalent load (the product of the daily water demand, V and the total pumping head, h) does not exceed 250m4/d. Hand pumps operate best in shallow wells (as deep as 15 meters). Pumping is more difficult with deeper wells. Depending on per capita water consumption, hand pumps can serve as many as 1,000 people in rural areas.22
Currently there is something of a buzz over fresh water production for many of the worlds poor; programs have been started by organizations like UNICEF and more are surely on the way. This is a future hot market as long as the technology is adaptable, and indeed some are already making a difference.
1.2.2Existing Products
The Rope Handpump (taken from Community Rope Pumps in Nicaragua)
The rope pump production, marketing and introduction started in Nicaragua through a privateenterprise effort. Two ex-fieldworkers of a UNICEF sponsored intervention continued thedevelopment of the rope pump (originally developed by a Belgian technician29) in 1990 as they noticed the high social acceptance by the users ofthe first trial within this project. They captured the social acceptance of the product by thepopulation and gave it continuity. The social acceptance in this stage was based already on itsefficiency. The pump had to win it from the rope and bucket, traditionally used to fetch waterfrom the wells, and so it did.21
The rope handpump can be classified as a positive displacement pump, in which water is lifted by achain of washers. The rope pump produces a constant output, unlike the pulsating flow ofconventional piston pump. It has a good efficiency and the design is not critical. If modern plasticsare used, resistant against wear, it has proven highly reliable and is easily maintained and repaired bypeople in the rural areas.
The pump functions well at groundwater depthsof up to 50 meters.Due to the simple and sturdy design of the pump, maintenance needs are very limited and can easily be handled bythe community or local artisan. The rope itself is the most likely part to break down, and can either be easily andcheaply replaced locally or patched up without difficulty. Makeshift repairs do not significantly detract frompump performance.
One of the keys to the rapid spread of the rope pump in Nicaragua has been its low cost allied to its reliability and low maintenance needs. A study performed for the WSP found that the annual maintenance cost of the rope pump never exceeded $10 (and in fact was less than $5 in all but one area (surveyed). By comparison, the annual maintenance cost for other pumps, predominantly India Mark IIs, ranged between $59 and $107.
In summary, the rope pump has the following strong points:
- Maintenance and repair is relatively simple, does not involve complex or expensive tools andcan be done by the user.
- The diameter required for the riser pipe can be kept small, thanks to the non-pulsating flow.
- The pipe walls can be thin because the loads on the riser pipe are low both in axial and radialdirections.
- The resulting total weight of about 10 kg is very low, compared to the weight of a classicalpiston pump (50 to more than 100 kg); this makes installation and lifting for maintenance andrepair much more easy.
- It has a minimum of moving parts, which are not very critical: no valves, valve seatings, norcomplex bearings are used.
- The volumetric efficiency of the rope handpump is reported to be 70 % [1] and about 85%for larger rope pumps [24].
- The use of plastic parts, concrete and ceramics makes the pump highly insensitive tocorrosion.
- The pump can be installed on a narrow tube well, just like a piston pump; the ½" rope pumpcan be installed on a 2" tube well.
- It is cheap: US$ 49,- to $ 90,-, depending on the specific pump type and pumping depth.
Figure1:The Rope Pump. The principal elements of the rope pump are a pulley wheel, a rope with pistons attached, a pipe that enters the well, and at the base of this pipe, a guidance device for the rope. As the crankshaft is turned the rope drags the pistons up the pipe, trapping the water above them and ejecting it at the surface.
The AMEC Rope Windpump (taken from Dissemination of the Nicaraguan Rope Windpump Technology)
The rope windpump can be conceived as an extension of the rope handpump. The mechanics of the rope windpump is easy to understand. A rope pump, similar to a rope handpump but somewhat larger and sturdier, is connected to a wind rotor on top of a tower. The transmission consists of a large rope that turns in a loop over a top (rotor) pulley and a bottom pulley on the pump shaft. If the wind is blowing strong enough, the rotor starts turning and operates the pump (see Figure 2).
The rotor head carries the rotor and a tail arm with a vane. The head assembly can turn freely around a vertical (or "yawing") axis. At low wind speeds, the tail vane directs itself parallel to the wind, turning the rotor automatically into the wind to make optimum use of the available energy in the wind. At higher wind speeds, the tail vane acts as a safety system to turn the rotor out of the wind. In this situation, the tail vane is lifted towards a horizontal position by the wind, which allows the eccentrically placed rotor to turn the head out of the wind. This limits the speed of the rotor to a safe value, even in very high wind speeds.
At this moment there is one limitation in the concept of the AMEC/CESADE rope windpump. The transmission rope limits the rotor head in its movements to turn itself into the wind, since it does not pass through the centre line (the yawing axis) of the tower but outside of it. To avoid the rope getting entangled with the tower if the rotor yaws too far from the "neutral" position (the right side in Figure 2) by a strong change in wind direction, the design is such that the rope runs of the top pulley. This behaviour is safe, but requires someone to readjust the rope. The rope windpump design is therefore more appropriate as the wind direction is more stable. This is not always the case.
The standard type rope windpump produced by AMEC is officially known as the H-270 and is the model shown in the figure. The number "270" refers to the maximum freedom of the rotor head to orientate itself into the wind (which is 135° both directions). It the wind comes from the back, the rope is pushed against the tower and runs off the pulley as described before. This makes the type more appropriate for regions with "unidirectional" winds (coming mainly from one direction). In many regions in Nicaragua, the wind direction is predominantly northeast during most of the year. The H-270 exists in three different models with a rotor diameter of 8, 10 and 12 feet. Towers are offered with a height of 8, 10 or 13 m. The nomenclature used is for example H-270-8-10 (or briefly H-8-10) to indicate a windpump with an 8' rotor on top of a 10-meter tower.
AMEC's second windpump type has a head that can rotate over a full circle (360) and has been developed for application in more variable wind regimes. This model, the H-360, is known as the multigiratorio, (literally "one that can make several turns"). The name is somewhat elusive however. At a half turn of the rotor (180out of the "neutral" position), the upward moving transmission rope touches the downward going one. As this contact causes rapid wear, the rotor head must be brought back into its original position by hand. This means that also the multigiratorio cannot be left unattended for a long time, although it can return into the original position by the wind itself. 23
Figure 2: Layout of the AMEC H-270 rope windpump, based on [16]. Indicated are the following components: the rotor (a); the head assembly and yaw bearing (b); the top pulley (c); the tail vane (d); the control rope (e); the tower (f); the transmission rope (g); the tower (h); the handle for manual pumping (i); the pump shaft transmission pulley (j); the main shaft (k); the pump pulley (l); the pump discharge tube (m).
Table 1: The different windpump models in production by workshop Aerobombas de Mecate in Managua (AMEC). The output figures are based upon the documentation provided by the manufacturer, for a wind speed of 5 m/s
1.3Design Objectives
With our example being AMEC and their H-10 (360) rope windpump, our design objectives were guided by the stats listed in Table 1. We haveadded some further objectives that were not quantified in the AMEC description but nonetheless will guide toward a practical and acceptable alternative to the rope windpump. Our objectives are outlined below in Table 2 and described in the section below.
Objective / Relationship / ValueHEQ / >= / 216m4/d
Max. pumping depth / >= / 30m
Min. wind speed / = / 3m/s
Size / 10m tall
Cost / =< / $750 ex. factory
Reliability / >= / 1 week unattended
Simplicity / 50 different parts
Quality / = / high
Recycled parts / >= / 20%
Efficiency / >= / 20% wind
Durability / >= / 10 yr. lifespan
Maintenance / = / Easy, routine
Weight / 300lbs.
Aesthetics / = / Appealing
Table 2: Outline of design objectives for water pumping system
1.3.1Sizing System
Installing the best system without a reliable water source is a waste of financial resources. Designing a system without estimating the realistic water resource might result in insufficient water supplies or unnecessary financial expenditures for an oversized system. Undersizing the pumping system can waste resources when there is demand for water for purposes other than the domestic water supply, such as irrigation.22
Following the guidelines laid out in Understanding Wind Energy for Water Pumping, the steps for sizing a system were followed in order to both double check AMEC’s numbers and to better understand the scale our system.
1.3.1.1Assess the water requirement
In a report issued by Energy forSustainable Development group it is stated that the daily volume of water required by a village of 500 is 20m3/day.sourceConversion of AMEC’s numbers, 12l/min, 20l/min, and 40l/min, and assuming 12 hour operation, the total daily outputs are 8.64m3/day, 14.4m3/day, and 28.8m3/day.
From these calculations, it is clear that AMEC’s system is appropriately sized for a community windpumping application. Our system should produce a comparative amount: 15l/min at the same windspeed and depth of 5m/s and 10m respectively, just to push the envelope a little. This comes to a total hydraulic equivalent load of 216m4/day, which is nearing the maximum for a handpump alone.
1.3.1.2Find Pumping Depth
Remaining consistent with our goal to compete with the AMEC windpump, our system should operate up to a pumping depth of 20m at a comparable performance. However, since the rope pump is reported to work to depths of 50m, we also plan to test our model for use at this depth and provide information as to the feasibility for using our system for deep well water extraction.
1.3.1.3Evaluate Wind Resource
Although AMEC lists 5m/s as their tested wind speed, this is not a reasonable approximation for constant wind speed 24 hrs/day. It is true that during the daytime hours this speed will likely be reached, but during the nighttime the wind tends to slow down. Taking 3m/s asthe speedof fringe wind conditions, we will optimize for 5m/s, but will make sure our system operates effectively at 3m/s.
1.3.1.4Estimate Size of Wind Machine
The size of our wind machine should be comparable to that of AMEC. The height will be a critical factor in transformation and installation, and our system should therefore be shorter or equal to the height of the AMEC system.
1.3.2Other Objectives
After taking into consideration the available resources (including what is available and what is needed), the possible solutions we will be considering (including what they are capable of and what is a reasonable expectation), and the design to manufacturing transformation (including what is ideal and what can actually be manufactured), we have come up with values for our design objectives. They are listed below and should provide a datum by which we can evaluate our final design and should be useful in steering us in the selection of an appropriate design.